When removing a task that was on home, put home on top.

Killing an app that was launched from home was not relaunching home.
Previous situations relaunched the next app (i.e. home) based on the
task flag. However, when an app dies the relaunch is deferred until
the TaskRecord has long been forgotten. This fix rearranges the stacks
immediately upon the TaskRecord being removed from the stack. Then the
next resumeTopActivities() call will start the home task.

Fixes bug 11189555.

Change-Id: I0e09350a7db55ea8b38cce7bf4b69923a6b99494